1. Field of the Invention
The present invention relates to a thermal printer having a shutter unit. More particularly, the present invention relates to a thermal printer having a shutter unit with which fixing rays from a photo fixer can be adjusted, and recording material can be used effectively without waste.
2. Description Related to the Prior Art
A color thermal printer is used with color thermosensitive recording material, which includes a support and at least three thermosensitive coloring layers overlaid thereon. The coloring layers are yellow, magenta and cyan coloring layers. Among the three, the yellow coloring layer is positioned the farthest from the support, and has the highest heat sensitivity. The cyan coloring layer is positioned the nearest to the support, and has the lowest heat sensitivity.
The thermal printer includes feeder rollers, a thermal head, a photo fixer and the like. The feeder rollers feed the recording material. The thermal head presses and heats the recording material, to develop color. The photo fixer accommodates an electromagnetic source, and emits electromagnetic fixing rays. The thermal head and the photo fixer are arranged in a feeding direction of the recording material.
A certain type of the thermal printer is used with the recording material in a continuous form that is wound in a form of a recording material roll. In the thermal printer, the recording material is unwound from the recording material roll, and subjected to thermal recording and photo fixation. A recording region of the recording material is provided with a full-color image, and cut by a cutter to obtain a sheet as a print. The sheet is ejected from the thermal printer. An unused region of the recording material remaining after the cutting is wound back to the recording material roll. The unused region having been adjacent to the sheet will be used in next operation of printing.
To fix the recording region in a regularized manner electromagnetically, the fixing rays must be applied to the recording region until a rear end of the recording region moves past the photo fixer. However, the fixing rays are applied also to the unused region. The unused region cannot be used for next operation of producing a print. This is waste of the recording material. In view of this, there is a suggestion in JP-A 10-067128, in which the thermal printer has a mechanical shutter for inserting a shutter screen in a space between the photo fixer and the recording material in synchronism with feeding of the recording material. This prevents the fixing rays from striking the unused region.
However, the mechanical shutter disclosed in the above document is structurally complicated due to the great number of incorporated parts. Efficiency in using a space is specifically low because of the mechanical shutter. A size of the thermal printer becomes remarkably large.
In view of the foregoing problems, an object of the present invention is to provide a thermal printer having a shutter unit with which fixing rays from a photo fixer can be adjusted, and recording material can be used effectively without waste.
In order to achieve the above and other objects and advantages of this invention, a thermal printer includes a feeder for feeding thermosensitive recording material through a feeding path. A thermal head operates for thermal recording of an image in a recording region of the recording material being fed, wherein an unused region is defined outside the recording region. A photo fixer fixes the image on the recording material by application of electromagnetic rays thereto. A liquid crystal shutter unit is disposed between the photo fixer and the recording material, and includes plural shutter segments, wherein the plural shutter segments are arranged in a predetermined pattern, and changeable between an opaque state and a transparent state independently from one another, and when in the opaque state, block the electromagnetic rays, and when in the transparent state, cause the electromagnetic rays to pass. A controller controls the liquid crystal shutter unit in synchronism with the feeder, sets at least one of the shutter segments in the transparent state if the at least one is opposed to the recording region in feeding of the recording material, and sets at least one of the shutter segments in the opaque state if the at least one is opposed to the unused region in feeding of the recording material.
The recording material is continuous, supplied in a wound form of a recording material roll, and the unused region is positioned nearer to the recording material roll than the recording region. Furthermore, a cutter cuts the recording material by the image after the recording region is fixed.
The thermal head extends crosswise to the feeding path. The shutter segments respectively extend crosswise to the feeding path, and are arranged in a direction along the feeding path.
The liquid crystal shutter unit includes first and second groups of electrodes, the first and second groups being connected with the controller, and disposed opposite to each other with reference to the feeding path.
Furthermore, a cooling unit or heat dissipating unit is disposed between the photo fixer and the liquid crystal shutter unit, for passing the electromagnetic rays, and for dissipating heat generated by the photo fixer.
The photo fixer includes a fluorescent lamp, and the electromagnetic rays are ultraviolet or visible.
The cooling unit or heat dissipating unit contacts a ray emitting surface of the photo fixer, and has a size larger than the ray emitting surface.
The cooling unit or heat dissipating unit includes a cooling unit casing disposed to extend crosswise to an optical path of the electromagnetic rays from the photo fixer to the liquid crystal shutter unit. Transparent fluid has high heat conductivity, is enclosed in the cooling unit casing.
The cooling unit casing includes a panel portion positioned backwards with reference to the optical path. A connection opening is formed in the panel portion, and has the photo fixer fitted therein. The transparent fluid contacts the ray emitting surface.
The cooling unit casing includes a panel portion positioned forwards with reference to the optical path, provided with the liquid crystal shutter unit secured thereto. A first opening is formed in the panel portion, for constituting the optical path.
The transparent fluid is ethylene glycol.